All credits go to mshkrebtan, this information is almost a copy (with minor fixes) from:
https://gist.github.com/mshkrebtan/407786e334847544b40e7d6a8a53d247
a)Enable support for 32-bit executables
Add the i386 architecture to the list of dpkg architectures :
sudo dpkg --add-architecture i386
Install the libraries required to execute ELF-32 executables:
sudo apt-get update
sudo apt-get install libc6:i386 libncurses5:i386 libstdc++6:i386
b)Install Firefox 52 ESR (32-bit)
Beginning with Firefox 52 (released March 2017), plug-in support is limited to Adobe Flash, and drops support for NPAPI, impacting plugins for Java, Silverlight, and other similar NPAPI based plugins. Hence you need the ESR release. You can read more on that here: https://www.java.com/en/download/help/firefox_java.xml
Download Firefox ESR for Linux (32-bit) from https://www.mozilla.org/en-US/firefox/organizations/all/
Unpack it to somewhere, for example to /opt/webex/:
sudo mkdir -p /opt/webex/
sudo tar -xjvf firefox*esr*.tar.bz2 -C /opt/webex/
Install the libraries required for Firefox (i386) to run smoothly:
sudo apt-get install \
libgtk-3-0:i386 \
libasound2:i386 \
libdbus-glib-1-2:i386 \
libxt6:i386 \
libxtst6:i386 \
libcanberra-gtk-module:i386 \
libcanberra-gtk3-module:i386 \
topmenu-gtk3:i386
c) Install 32-bit JRE
Download Oracle JRE for Linux (a tar.gz archive for x86 architecture) from: http://www.oracle.com/technetwork/java/javase/downloads/jre8-downloads-2133155.html
Unpack it to /opt/webex/:
sudo tar -xzvf jre*linux-i586.tar.gz -C /opt/webex/
sudo mv /opt/webex/jre* /opt/webex/jre
d)Enable Java support in Firefox
Create symbolic links for the Java browser plugin libraries:
sudo mkdir /opt/webex/firefox/plugins/
sudo ln -s \
/opt/webex/jre/lib/i386/libawt.so \
/opt/webex/jre/lib/i386/libjawt.so \
/opt/webex/jre/lib/i386/libnpjp2.so \
/opt/webex/firefox/plugins
e)Install the libraries required for Webex to run
sudo apt-get install \
libpangoxft-1.0-0:i386 \
libxft2:i386 \
libpangox-1.0-0:i386 \
libxmu6:i386 \
libxv1:i386 \
libasound2-plugins:i386
f)Create a Firefox launch script
cat << 'EOF' | sudo tee /opt/webex/firefox.sh
#!/bin/bash
export ENV_HOME=/opt/webex
export FIREFOX_HOME=$ENV_HOME/firefox
export MOZ_PLUGIN_PATH=$ENV_HOME/firefox/plugins
export JAVA_HOME=$ENV_HOME/jre
export PATH=$JAVA_HOME/bin:$PATH
#export JPI_PLUGIN2_DEBUG=1
$FIREFOX_HOME/firefox --no-remote -P
EOF
This script will start a new instance of Firefox with the ProfileManager. Choose an existing Firefox profile or create a new one.
You might want to specify a specific profile to start with. Just add the profile name after the -P flag.
Don't forget to make the script executable:
sudo chmod a+x /opt/webex/firefox.sh
You might want to create a symlink, like this:
sudo ln -s /opt/webex/firefox.sh /usr/local/bin/firefox-i386
4.a) Start a Webex session
Launch the script and join a Webex session [https://www.webex.com/test-meeting.html]:
$ firefox-i386
If webex.com sends you a jnlp file and Firefox asks what to do with it, just download it. Further, in the Firefox Preferences > Applications, set the action for JNLP files: they should be opened with javaws (Java Web Start) which can be found here:
/opt/webex/jre/bin/javaws
4.b) (Optional) Install the missing libraries required by Webex
Find out what required libraries are be missing (note that the session number may be different):
ldd ~/.webex/T32_UMC/*.so | grep "not found"
You can use http://packages.ubuntu.com/ to find out which packages contain the libraries.
It is OK to have libjawt.so being not found.